It has heretofore been proposed that closures be provided for containers wherein the closures on the container by an integral hinge. Conventionally, such closures rely on tension on the hinge to produce a snap action. Typical constructions are shown in U.S. Pat. Nos. 3,628,215, 3,629,901, 3,933,271, 4,047,495, 4,386,714.
In U.S. Pat. No. 4,638,916, a closure with a snap type hinge cap comprises a first part adapted to interengage with the open neck of a container, a second part forming a cap and an integral hinge interconnecting the first and second parts comprises a base wall and a peripheral skirt. A pair of hinge straps extends from the skirts and are positioned on opposite sides of the integral hinge. The radial length of the pair of hinge straps is less than the length of the arc through which the second cap part moves to and from and closed position relative to the first part such that the pair of straps stretch to function as springs. The ends of the pair of straps are attached to the skirts radially inwardly of the periphery of the skirts.
Among the objectives of the present invention are to provide an improved closure with a snap-type hinge cap with improved performance and longer life; which reduces or eliminates excessive stress on the straps during opening and closing which might cause breaking; and which can be made with minimal added cost.
In accordance with the invention, a closure with a snap type hinge cap comprises a first part adapted to interengage with the open neck of a container, a second part forming a cap and an integral hinge interconnecting the first part and second part. Each of these parts comprises a base wall and a peripheral skirt. A pair of hinge straps extend from the skirts on opposite side of the integral hinge. The ends of the straps are straight and lie in substantially the same plane when the first part and second part in fully open position. Each strap has a portion intermediate the ends which extends out of the plane. Each strap is untensioned when the first part and second part are in fully open position. The intermediate portions of the straps extend axially in one direction. In one form the intermediate portions of said straps are curved in cross section. In another form intermediate portions of said straps are V-shaped in cross section.